Light receiving device for optical radar, optical radar, and meteorological observation optical radar

Abstract

The invention provides a light receiving device for an optical radar, which can reduce the influence of simultaneous counting loss and crosstalk on the measurement result. Provided is a light receiving device for an optical radar that detects scattered light of laser light, the light receiving device being provided with: a light splitting element that splits received light so that the received light is dispersed in one axial wavelength; an optical element for making the wavelength resolution of light having a relatively high intensity in the wavelength dispersion axis direction of the split light higher than the wavelength resolution of light having a relatively low intensity in the wavelength dispersion axis direction of the split light among the split light; and an array detector that detects light whose spectrum has changed through the optical element.

Description

Technical Field

[0001] The present invention relates to a light receiving device for an optical radar, an optical radar, and a weather observation optical radar. Background Art

[0002] An optical radar is a device that performs various measurements by irradiating a measurement space with laser light and measuring the time from the irradiation to the reception of reflected light, or analyzing the spectrum of scattered light of the laser light.

[0003] For example, Patent Document 1 discloses the following: using an optical radar as an observation means for observing the temperature distribution, water vapor concentration, and wind direction / speed of the sky. Patent Document 1 discloses a meteorological observation optical radar for observing scattered light of laser light, which includes a diffraction grating for diffracting rotational Raman scattered light included in the scattered light, a detector for detecting the diffracted rotational Raman scattered light, and a removal element for specifically removing elastic scattered light included in the scattered light.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2020 / 075869 Summary of the invention

[0007] Problems to be solved by the invention

[0008] The inventors have found the following problem: in the process of developing a light receiving device for optical radar, when an array detector is used for spectral analysis of received light, the relationship between the amount of light input in each detection channel and the signal value output becomes nonlinear (simultaneous counting loss), and measurement errors may occur due to crosstalk between adjacent channels of the array detector. In particular, it has been found that in optical radars that perform Raman spectrum analysis, such simultaneous counting loss and crosstalk are likely to affect the measurement results.

[0009] The present invention has been completed in view of the above-mentioned problems, and its object is to provide a light receiving device for an optical radar, an optical radar, and a meteorological observation optical radar that can reduce the influence of simultaneous counting loss and crosstalk on measurement results.

[0010] Means used to solve problems

[0011] An optical radar light receiving device involved in one embodiment of the present invention is a light receiving device for an optical radar that detects scattered light of a laser, and the light receiving device for an optical radar comprises: light that has been split in a manner so that the received light is dispersed along an axial wavelength; an optical element that makes the wavelength resolution of light with relatively high intensity in the split light higher than the wavelength resolution of light with relatively low intensity in the axial wavelength dispersion; and an array detector that detects light whose spectrum has been changed by the optical element.

[0012] The greater the difference in the photon flux density of the light received by each channel in the array detector, the greater the impact of simultaneous counting loss and crosstalk on the measurement results. The above-mentioned optical radar light receiving device has an optical element in the front section of the array detector that makes the wavelength resolution of light with relatively high intensity in the light split by the spectroscopic element higher than the wavelength resolution of light with relatively low intensity. In the above-mentioned optical radar light receiving device, through such an optical element, the intensity of light with relatively low intensity of the light split by the spectroscopic element is relatively increased, and the intensity of light with relatively high intensity is relatively reduced. Therefore, in the above-mentioned optical radar light receiving device, compared with the spectrum of the light split by the spectroscopic element, the difference in the intensity of the spectrum of the changed light becomes smaller due to the optical element, so the difference in the photon flux density of the light received by each channel in the array detector becomes relatively small, which can reduce the impact of simultaneous counting loss and crosstalk on the measurement results.

[0013] The light after the splitting may have a spectrum shape in which the intensity near the central wavelength is relatively high and the intensity near the spectrum end is relatively low. In this embodiment, the optical element makes the light L having a wavelength near the central wavelength of the spectrum in the splitting light c The wavelength resolution of the wavelength dispersion axis of the light after the spectral separation is higher than that of the light having a wavelength near the spectral end of the spectrum. e According to this aspect, when receiving rotation Raman or vibration Raman, it is possible to suitably perform spectrum analysis of the received light.

[0014] In the above aspect, the optical element is preferably configured to improve the light L c The wavelength resolution of the wavelength dispersion axis of the light after being split is reduced. e According to this method, the intensity of light with relatively high intensity is reduced, and the intensity of light with relatively low intensity is increased, so the influence of simultaneous counting loss and crosstalk on the measurement results can be further reduced.

[0015] In any of the above aspects, the optical element is preferably an aspherical lens, or a combination of an aspherical lens and one or more other optical elements. According to this aspect, for example, the optical system can be made smaller than a method using an aspherical mirror.

[0016] In the embodiment in which the optical element includes an aspherical lens, when the straight-moving direction of the light after being split is set as the z-axis direction and the wavelength dispersion axis direction of the light after being split is set as the y-axis direction, the aspherical lens is preferably arranged so that the optical axis is parallel to the light L when viewed from the x-axis direction orthogonal to the z-axis and the y-axis. c The optical paths of the optical axis are roughly consistent, and the aspheric lens makes the wavelength resolution of the light passing through the vicinity of the optical axis in the y-axis direction higher than the wavelength resolution of the light passing through the portion away from the optical axis in the y-axis direction. According to this method, an aspheric lens that is relatively easy to manufacture can be used.

[0017] In the embodiment using the aspheric lens arranged as described above, the aspheric lens is preferably a cylindrical lens extending in the x-axis direction. According to this embodiment, the wavelength resolution of the dispersed light in the x-axis direction is not converted into a nonlinear shape.

[0018] In any of the above aspects, the spectroscopic element preferably includes a diffraction grating.

[0019] In any of the above-mentioned methods, the above-mentioned spectroscopic element is preferably a relay lens arranged just before the above-mentioned array detector. According to this method, even an existing optical radar light receiving device including an existing spectroscopic element can be used as an optical radar light receiving device of this embodiment by installing the spectroscopic element as the relay lens. In addition, the optical system of the relay lens is adjusted without adjusting the internal optical system of the light receiving device or by minimizing the internal optical system of the light receiving device, thereby making it easy to adjust the overall performance of the optical radar light receiving device.

[0020] The optical radar light receiving device can be suitably used for meteorological observation, and is particularly suitable for applications such as analyzing rotational Raman spectra and vibrational Raman spectra.

[0021] An optical radar according to one embodiment of the present invention includes an irradiation device for irradiating laser light and the above-mentioned optical radar light receiving device. Since such an optical radar includes the above-mentioned optical radar light receiving device, it is possible to reduce the influence of simultaneous counting loss and crosstalk on the measurement results. As an optical radar light receiving device, when the above-mentioned optical radar light receiving device for meteorological observation is used, it can be used as a meteorological observation optical radar.

[0022] The laser irradiated by the irradiation device in the above-mentioned weather observation optical radar is preferably a laser in the UV region. According to this embodiment, it is suitable to obtain Raman spectra of nitrogen molecules, oxygen molecules, water molecules, etc. In addition, the above-mentioned weather observation optical radar is preferably used for air temperature measurement.

[0023] Effects of the Invention

[0024] According to the present invention, it is possible to provide a light receiving device for an optical radar, an optical radar, and a weather observation optical radar that can reduce the influence of simultaneous counting loss and crosstalk on measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A diagram showing the structure of an optical radar in an embodiment.

[0026] Figure 2 A diagram showing the structure of a light receiving device for an optical radar according to a first embodiment.

[0027] Figure 3 (A) A stereoscopic view and (B) a top view of an example of the configuration of an aspherical lens in a light receiving device for an optical radar.

[0028] Figure 4 A schematic structural diagram of a light receiving device for an optical radar according to a second embodiment.

[0029] FIG. 5(A) is a diagram showing the configuration of a light receiving device for an optical radar according to a third embodiment.

[0030] FIG5(B) is another diagram showing the configuration of the light receiving device for optical radar according to the third embodiment.

[0031] Figure 6 A diagram showing the structure of a weather observation optical radar equipped with a ground correction device.

[0032] Figure 7 (A) A schematic diagram, (B) a top view, and (C) a front view of the array detector showing a model in simulation using OpticStudio.

[0033] Figure 8 (A) shows a schematic diagram of the optical system, (B) an enlarged diagram, and (C) the results of an experiment in which a light-receiving device for an optical radar was used to confirm the focusing state.

[0034] Fig. 9 (A) Settings and (B) Results of a simulation of a cylindrical lens with concavoconvex surfaces introduced.

[0035] Fig.10 (A) is a schematic diagram of an optical system and (B) is a result of an experiment to confirm the focusing state of a light receiving device for an optical radar when a cylindrical lens with concavoconvexity is introduced.

[0036] Fig.11 (A) Settings and (B) Results of a simulation in which an aspherical lens was introduced.

[0037] Fig.12 (A) A top view of the model in the simulation when the optical element that changes the wavelength resolution is a relay lens, (B) a side view, and simulation results showing the change distribution of the wavelength resolution before and after incident on the (C) optical element are shown.

[0038] Fig.13 The wavelength of each channel of the array detector set in the simulation of air temperature measurement accuracy is shown.

[0039] Fig.14 The signal intensity distribution obtained in each detector setting is shown.

[0040] Fig.15 The results of temperature estimation without signal strength correction are shown in Figure 1. The straight lines formed by the points are the results of case-1, case-2, case-3, case-4, and case-5 in order from the top.

[0041] Fig.16 This is the result of the estimation accuracy when the air temperature is assumed to be 250K to 320K for case-5.

[0042] Fig.17 Indicates the accuracy of temperature estimation after signal strength correction. The straight line formed by the points in the left figure (T=273) is the result of case-1, case-2, case-3, case-4, case-5 and case-6 from the top. The straight line formed by the points in the right figure (T=300) is the result of case-1, case-2, case-3, case-4, case-6 and case-5 from the top when the x-axis is 100MHz.

[0043] Fig.18 Indicates the deviation after signal strength correction. The straight lines formed by the points are the results of case-1, case-2, case-3, case-4, case-5, and case-6 in order from the top. DETAILED DESCRIPTION

[0044] Hereinafter, this specific embodiment (hereinafter referred to as "this embodiment") is described in detail with reference to the accompanying drawings, but the present invention is not limited thereto and various modifications are possible without departing from the gist of the present invention. In the following description of the drawings, the same or similar parts are marked with the same or similar reference numerals. The drawings are schematic diagrams and may not be consistent with actual dimensions, ratios, etc. Sometimes, the relationship between the dimensions and the ratios between the drawings are different.

[0045] [Optical radar]

[0046] Figure 1 The basic structure of the optical radar in this embodiment is shown in FIG. Figure 1 As shown, the optical radar 100 of this embodiment generally includes an irradiation device 1 and a light receiving device 2.

[0047] like Figure 1 As shown, the irradiation device 1 mainly includes a laser device 10, a mirror 12, and a beam expander 14. The irradiation device 1 has a function as a light emitting unit for emitting laser light having a specific wavelength.

[0048] The laser device 10 is a light emitting unit that emits a laser beam of a predetermined wavelength. Depending on the purpose of the optical radar, the wavelength of the laser can be appropriately selected by combining a wavelength conversion element such as a double-wave crystal or a four-wave crystal. The mirror 12 is an optical element that reflects the direction of the output laser beam toward the light emission direction of the irradiation device. The beam expander 14 is an optical element that expands the beam diameter of the laser beam that is injected as parallel light and outputs it as the emitted light Lo.

[0049] The light receiving device 2 includes a light receiving unit 20, an aperture 21, a spectroscopic element 22, and a signal processing unit 23. The emitted light L0 emitted by the irradiation device 1 is reflected and / or scattered by obstacles and components in the atmosphere, and a part of it is incident on the optical radar 100 as incident light Li. The light receiving device 2 has a function of detecting and analyzing the incident light Li.

[0050] The light receiving unit 20 allows the incident light Li to enter and converges the light beam. The aperture 21 allows the converged incident light Li to pass through and removes unnecessary light components. The spectroscopic element 22 separates the received light in a manner that disperses the wavelength along one axial direction. The spectroscopic element 22 is not particularly limited as long as it has the above-mentioned function, but examples thereof include a diffraction grating and a prism.

[0051] The signal processing unit 23 analyzes the light dispersed by the spectroscopic element 22, for example, analyzes the spectrum of the received light. The signal processing unit 23 analyzes the spectrum of the received light and obtains the composition and temperature of the atmosphere in the sky based on the intensity of scattered light of multiple wavelengths.

[0052] The signal processing unit 23 includes an optical element and an array detector described below. The optical element performs the conversion described below on the light after being split by the spectroscopic element 22. The light that has passed through the optical element is detected by the array detector. The array detector has a plurality of detection units, and each detection unit (channel) detects light quanta individually. In the array detector, each detection unit can be configured with equal width and equal intervals. The width of each detection unit can be, for example, greater than 0.5 mm and less than 2.0 mm. In such an array detector, for example, when detecting light that is split at equal intervals, each detection unit can detect light with each wavelength of the split light, and can analyze the spectrum of the split light by corresponding to each channel and each wavelength. As array detectors, for example, photomultiplier tube (PMT) arrays, avalanche photodiode arrays, and electron multiplier charge coupling devices (EMCCDs) are listed.

[0053] The results processed and analyzed by the signal processing unit 23 can be displayed on a display unit also provided in the optical radar 100 , or can be transmitted wirelessly or by wire to an information processing device connected to the optical radar 100 , or can be fed back by the irradiation device 1 .

[0054] [Light receiving device for optical radar]

[0055] The following is a detailed description of the structure of the light receiving device 2. The light receiving device 2 is a light receiving device for an optical radar of the present embodiment, and the light receiving device 2 includes: a spectroscopic element that splits the received light in a manner that disperses the wavelength along one axial direction; an optical element that makes the wavelength resolution of the light with relatively high intensity in the split light higher than the wavelength resolution of the light with relatively low intensity in the split light with respect to the axial direction of the wavelength dispersion; and an array detector that detects the light whose spectrum has been changed by the optical element. The light whose spectrum has been changed by the optical element may be the light that has passed through the optical element or reflected from the optical element.

[0056] The optical element can improve the wavelength resolution of light with relatively high intensity and reduce the wavelength resolution of light with relatively low intensity, and can also improve the wavelength resolution of both light with relatively high intensity and light with relatively low intensity (in this case, the wavelength resolution of light with relatively high intensity is further improved), and can also reduce the wavelength resolution of both light with relatively high intensity and light with relatively low intensity (in this case, the wavelength resolution of light with relatively low intensity is further reduced). In the context, wavelength resolution can also be referred to as wavelength resolution. The optical element is preferably an aspheric lens, or a combination of an aspheric lens and one or more other optical elements. For example, it can be a combination of an optical element with negative power such as a concave lens and an aspheric lens, or it can be a combination of one or more aspheric lenses and one or more spherical lenses. In the case where the optical element is a reflective optical element such as a mirror, it is preferably a material or coating with high reflectivity within the spectral range of the measured object. In the case where the optical element is a transmissive optical element such as a lens, it is preferably applied with a reflection prevention film on both sides of the optical element.

[0057] (First embodiment)

[0058] Figure 2 The optical radar light receiving device of the first embodiment is shown. Figure 2 As shown, the optical radar light receiving device of the first embodiment includes a light receiving unit 20, an aperture 21, a spectroscopic element 22, an aspherical lens 231, an array detector 232, a concave mirror 241, and a concave mirror 242. The light incident from the aperture 21 is guided to the spectroscopic element 22 by the concave mirror 241. The spectroscopic element 22 is, for example, a diffraction grating. Figure 2 In the embodiment, the spectroscopic element 22 splits the incident light so as to disperse it along one axial wavelength in the plane.

[0059] The light split by the spectroscopic element 22 is guided to the aspheric lens 231 through the concave mirror 242. The spectroscopic spectrum of the incident light Li is projected onto the array detector 232 through the aspheric lens 231. The light incident on the aspheric lens 231 and the light irradiated on the array detector 232 have Figure 2 The aspherical lens 231 disperses the wavelength L of the light L having a relatively high intensity among the light separated by the light separation element 22. H The wavelength dispersion direction of the split light ( Figure 2 The wavelength resolution in the y-axis direction is higher than that in the case of relatively low intensity light L L On the other hand, in the conventional optical radar light receiving device, the light separated by the spectroscopic element 22 is guided to the array detector 232 through the concave mirror 242, and the spectroscopic spectrum of the incident light Li is projected onto the array detector 232 without passing through the aspherical lens.

[0060] An aspherical lens 231 is disposed between the optical path of the spectroscopic element 22 and the array detector 232, thereby reducing the difference in the photon flux density of the light received by each channel of the array detector 232 in the optical radar light receiving device of the first embodiment. H And light L L In both cases, light with a wavelength range Δλ is incident on n channels of the array detector (i.e., H In the example, the central wavelength is set to λ H , the injection in n channels has λ H ±Δλ / 2 wavelength light, in the light L L In the example, the central wavelength is set to λ L , the injection in n channels has λ L In this case, the aspheric lens 231 is arranged in front of the array detector 232, so that the light L H Injection in n H The channels have wavelengths of light in the range of Δλ. L Injection in n L Each channel has a wavelength of light in the range of Δλ. When this is the case, the light L H The wavelength resolution is higher than that of light L L The wavelength resolution of n H Greater than n L When the aspherical lens 231 is not configured, the light L H And light L L These two are detected by the same number (n) of channels. On the other hand, when the aspherical lens 231 is configured, n H Greater than n L , so the light L H Light L L Thus, the split light passes through the aspherical lens 231, and the light L H With light L L The difference in the photon flux density of the light received by each channel of the array detector 232 is reduced. As a result, the difference in the ratio of the simultaneous counting loss and the crosstalk in the signal value of each channel is also reduced, thereby providing a light receiving device for an optical radar that can reduce the influence of the simultaneous counting loss and the crosstalk on the measurement result.

[0061] Figure 3 FIG. 2 shows an example of a configuration method of the aspherical lens 231. Figure 3In FIG. 2 , the z-axis corresponds to the straight direction of the light split by the spectroscopic element and incident on the array detector 232, and the y-axis corresponds to the direction consistent with the wavelength dispersion axis of the split light. The aspherical lens 231 is arranged along the Figure 3 The cylindrical lens 231 is a cylindrical lens extending in the x-axis direction orthogonal to the y-axis and z-axis defined above. The aspherical lens 231 is a cylindrical lens extending in the x-axis direction orthogonal to the y-axis and z-axis defined above. Figure 3 The aspheric lens 231 is configured such that the optical axis (in a top view) is Figure 3 (B) is indicated by a single dotted line) and is approximately perpendicular to the detection surface of the array detector 232. Figure 2 The angles and positions of the light-splitting element 22, the concave mirror 241, and the concave mirror 242 are such that the split light is irradiated in a manner substantially parallel to the optical axis of the aspherical lens 231. It should be noted that in this specification, when the term "substantially" is used with respect to an angle, such as substantially vertical and substantially parallel, it means that the angle satisfying the conditions described is within the range of ±10°, preferably ±5°, and more preferably ±1°.

[0062] In the first embodiment, the incident light Li has a spectrum shape in which the intensity near the central wavelength is relatively high and the intensity near the spectral end is relatively low. As the incident light Li having such a spectrum, for example, Raman scattered light such as rotational Raman scattered light and vibrational Raman scattered light is listed. It should be noted that the spectrum shape of the light after the splitting does not necessarily require the peak wavelength to be consistent with the central wavelength. For example, in the case of a light having a central wavelength λ X , and the spectral width Δλ X In the spectrum (the difference between the maximum wavelength and the minimum wavelength contained in the split light), there is λ X ±Δλ X The intensity of light with a wavelength in the range of λ / 4 exceeds 50% of the integrated intensity of the entire spectrum, preferably 60% or more, more preferably 65% ​​or more of the spectrum, or the peak wavelength may be at λ X ±Δλ X / 4 range, etc. The light passing through the aspherical lens 231 may be Raman scattered light such as rotational Raman scattered light and vibrational Raman scattered light, or may be light from which elastic scattered light components are exclusively removed from such Raman scattered light.

[0063] like Figure 3 As shown in (B) in the first embodiment, light L having a wavelength near the center wavelength of the spectrum of light incident on the aspherical lens 231 is c Light L having a wavelength near the spectral end of the spectrum passes through the vicinity of the center (optical axis) of the aspherical lens 231. eThe angles and positions of the beam splitter 22, the concave mirror 241, and the concave mirror 242 are arranged in a manner near the end of the aspherical lens 231. That is, the aspherical lens 231 is arranged so that the optical axis is aligned with the light L when viewed from the x-axis direction. c The wavelength near the center wavelength may be, for example, a wavelength in the range of center wavelength ± (half-value full width) / 2, or a wavelength in the range of center wavelength ± (spectral width) / 2.

[0064] In addition, Figure 3 In (B), the aspherical lens 231 is a lens that makes the wavelength resolution of the light passing near the optical axis in the y-axis direction higher than the wavelength resolution of the light passing through the portion away from the optical axis in the y-axis direction. c Light L having a wavelength near the end of the spectrum passes near the optical axis. e The aspherical lens 231 makes the light L pass through the portion far from the optical axis in the y-axis direction (near the end of the aspherical lens 231). c The wavelength resolution in the y-axis direction is relative to the wavelength of light L e Here, the light L c Light L e The relative strength is high, so according to Figure 3 The configuration shown can make the wavelength resolution in the axial direction of wavelength dispersion of the dispersed light having a relatively high intensity higher than the wavelength resolution in the axial direction of wavelength dispersion of the dispersed light having a relatively low intensity.

[0065] For example, by appropriately selecting the two surfaces of the lens when viewed from the x-axis direction, it is possible to design an aspheric lens that makes the wavelength resolution of light passing through the vicinity of the optical axis in the y-axis direction higher than the wavelength resolution of light passing through the portion away from the optical axis in the y-axis direction. For example, it is preferable to design an aspheric lens by adjusting the coefficient α of the aspheric lens function shown in formula (1), the cone coefficient k, and the curvature radius R. Here, the z-axis and the y-axis are set to Figure 3 In the directions shown, i is an integer from 1 to 7.

[0066] [Number 1]

[0067]

[0068] As an example of an aspheric lens function, for example, the surface of the array detector side of the aspheric lens is set to a function of k=0, i=1, and the other surface is set to a function of R=∞, k=0, i=1 to 3. In addition, the optical radar light receiving device may have a plurality of aspheric lenses, or the concave mirror 242 may be set to an aspheric mirror instead of using an aspheric lens. In addition, it may be a combination of an aspheric lens and an aspheric mirror. The aspheric lens 231 may be a lens having a larger distortion in the y-axis direction than a spherical lens.

[0069] (Second Embodiment)

[0070] Figure 4 A schematic structural diagram of a light receiving device for an optical radar according to a second embodiment. Figure 2 The optical radar light receiving device of the first embodiment shown is an aspherical lens in which the optical element for changing the wavelength resolution is arranged in the front section of the array detector. Figure 4 The light receiving device for an optical radar of the second embodiment shown is different from the first embodiment in that an optical element for changing the wavelength resolution is arranged at a relay lens immediately before the array detector.

[0071] More specifically, in Figure 2 In the first embodiment shown in the figure, an aspherical lens 231 is arranged in front of the imaging position of the light splitting element 22 by the concave mirror 242. Figure 4 In the second embodiment shown in (A) of FIG. 1 , an optical element 233 is arranged as a relay lens at a rear section of the imaging position of the spectral element 22. In this way, by arranging the optical element 233 as a relay lens at a rear section of the imaging position of the spectral element, the optical system of the spectral element 22 is not adjusted, or the optical system of the spectral element 22 is minimized, and the optical system of the optical element 233 is adjusted, the overall performance of the optical radar light receiving device can be easily adjusted. That is, the optical element 233 is arranged as a relay lens in the existing optical radar light receiving device, and an array detector is arranged immediately thereafter, thereby making it relatively easy to implement the second embodiment.

[0072] Figure 4 The optical radar light receiving device of the second embodiment shown in (A) of FIG. 1 includes an aperture 21, a spectroscopic element 22, an optical element 233, and an array detector 232. Figure 4 Although omitted in the figure, the optical radar light receiving device of the second embodiment can be provided with a light receiving unit 20 and other optical elements in the same manner as the first embodiment. As other optical elements, the optical elements described in this specification can include, for example, mirrors (plane mirrors, concave mirrors), lenses, etc.

[0073] exist Figure 4 In (A), similarly to the first embodiment, the optical element 233 makes the light L with relatively high intensity H The wavelength dispersion direction of the split light ( Figure 2 The wavelength resolution in the y-axis direction is higher than that in the case of relatively low intensity light L L The wavelength resolution in the y-axis direction.

[0074] Figure 4 (B) and Figure 4 (C) means Figure 4 An example of the structure of the optical element 233 in (A) is a top view and a side view. Figure 4 (B) and Figure 4 As shown in (C) in FIG. 1 , the optical element 233 may be composed of a plurality of lenses. Preferably, at least one of the plurality of lenses is an aspherical lens. In addition, the plurality of lenses may include a lens with positive refractive power and / or a lens with negative refractive power.

[0075] From the viewpoint of easy design and manufacturing, the optical element 233 is preferably composed of a plurality of cylindrical lenses. Figure 4 The optical element 233 may extend in the y-axis direction (the wavelength dispersion direction of the light after the splitting), or may extend in the x-axis direction (the straight-ahead direction of the light, i.e., the z-axis direction, which is orthogonal to the y-axis direction). Preferably, the optical element 233 includes a cylindrical lens extending in the y-axis direction, and a cylindrical lens extending in the x-axis direction. More preferably, the optical element 233 includes a cylindrical lens having an aspherical surface extending in the x-axis direction, a spherical cylindrical lens extending in the x-axis direction, and a spherical cylindrical lens extending in the y-axis direction. The cylindrical lens having an aspherical surface extending in the x-axis direction may be arranged at the frontmost section (i.e., optically closest to the splitting element).

[0076] exist Figure 4 In the second embodiment shown, the distance between the spectroscopic element 22 and the array detector 232 (physical distance along the optical path) can be longer than the distance between the spectroscopic element 22 and the array detector 232 in the first embodiment. Figure 4 In the second embodiment shown, the array detector 232 may be disposed at a rearward position relative to the original imaging position of the light separation element 22 .

[0077] (Third Embodiment)

[0078] In addition to the above-mentioned structure, the optical radar light receiving device of this embodiment may also have a structure for specifically removing a specific wavelength in the split light. Such a structure includes, for example, interference filters such as notch filters and bandpass filters, spatial filters, and slits.

[0079] 5(A) and 5(B), a method of having a slit as a structure for specifically removing a specific wavelength in the split light is described as a third embodiment. In the third embodiment, the same reference numerals are used for the same or similar structures as those in the first embodiment, and repeated descriptions are omitted.

[0080] The optical radar light receiving device of the third embodiment shown in FIG. 5(A) further includes a slit 25 , a mirror 26 , an additional spectroscopic element 27 , a concave mirror 243 , and a concave mirror 244 , and in this respect, it is different from the optical radar light receiving device of the first embodiment.

[0081] The slit 25 removes the transmitted light by allowing only a part of the light to pass through and emitting the rest of the light. The wavelength of the light to be removed can be appropriately selected by adjusting the setting position of the slit 25. The slit 25 is not particularly limited as long as it is an element that can remove light having at least a part of the wavelength, and for example, it can be an optical element that appropriately combines an interference filter and / or a spatial filter with a mirror.

[0082] The spectroscopic element 27 also separates the light separated by the spectroscopic element 22. The spectroscopic element 27 is, for example, a diffraction grating. As described above, by having two spectroscopic elements, the optical radar light receiving device of the third embodiment can perform very precise spectrum analysis.

[0083] The optical radar light receiving device of the third embodiment shown in FIG5(B) has a relay lens, that is, an optical element 233, instead of the aspheric lens 231. Furthermore, a removal element 29 is provided in the front section of the optical element 233. This is different from the optical radar light receiving device of the third embodiment shown in FIG5(A). If the removal element 29 is an element used to specifically remove a specific wavelength in the split light, it is not particularly limited, and can be, for example, an interference filter, a spatial filter, or a combination thereof. The structure and preferred method of the optical element 233 are the same as those described in the second embodiment.

[0084] In the optical radar light receiving device of the third embodiment shown in FIG5(B), as a first configuration for specifically removing a specific wavelength in the split light, the slit 25 is provided as a second configuration with a removal element 29. In this embodiment, the slit 25 and / or the removal element 29 can be omitted, and an element capable of removing light having at least a part of the wavelength can be used instead of the slit 25 (for example, an optical element in which a mirror is appropriately combined with an interference filter and / or a spatial filter).

[0085] In this way, when the relay lens, i.e., the optical element 233, is used as the optical element for changing the spectrum, there is a light-converging point between the light-splitting element 27 and the optical element 233, so a removal element 29 for removing light of a part of the wavelength can be provided near the light-converging point. According to the configuration shown in FIG. 5(B), there are advantages that the removal efficiency of light of a specific wavelength can be improved by the removal element 29, or light of a specific wavelength can be removed with a higher wavelength resolution than when only the slit 25 is used (the accuracy of the removed wavelength is improved).

[0086] [Weather Observation Optical Radar]

[0087] The above-mentioned optical radar and light receiving device for optical radar can be applied as a meteorological observation optical radar, especially a meteorological observation optical radar for temperature measurement.

[0088] like Figure 1 As shown, in the weather observation optical radar, the irradiation device 1 emits laser light into the sky. In addition, the light receiving device 2 receives light scattered by components in the atmosphere, such as water vapor (H2O) molecules, nitrogen (N2) molecules, and oxygen (O2) molecules.

[0089] The laser device 10 can emit, for example, laser light in the UV region. The laser device 10 can emit, for example, YAG laser light with a wavelength of 266 nm, 355 nm, or 532 nm, or can emit excimer laser light with a wavelength of 248 nm, 308 nm, or 351 nm. By using laser light in the UV region, the background light intensity based on daytime sunlight can be reduced.

[0090] The irradiation device 1 may include a precision air conditioner that keeps the dust level of the space including a part or the entirety of the optical path of the laser at a constant level or less. By having a precision air conditioner, damage to optical components can be suppressed and aging resistance can be improved. In addition, the irradiation device 1 may include a temperature regulating mechanism that keeps the temperature change of the optical components and the surrounding space at a constant level or less. Even by preventing the drastic temperature change of the optical system, damage to optical components can be suppressed and aging resistance can be improved. The laser damage threshold (laser density at which damage begins) of an optical element decreases as the wavelength becomes shorter, and the damage to the optical element generally increases. In particular, optical radars for meteorological observations are difficult to operate stably in lasers with wavelengths in the UVC region, but stable operation in this region can be achieved by having the above-mentioned configuration.

[0091] The light receiving device 2 can receive Raman scattered light scattered by components in the atmosphere such as water vapor (H2O) molecules, nitrogen (N2) molecules, and oxygen (O2) molecules. The Raman scattered light may be rotational Raman scattered light or vibrational Raman scattered light.

[0092] The light receiving unit 20 may be a telescope. The aperture of the telescope may be, for example, not less than 10 cm and not more than 60 cm, or not less than 10 cm and not more than 40 cm.

[0093] The light receiving device 2 preferably further includes a configuration for removing specific wavelengths, as in the optical radar light receiving device of the third embodiment. According to this mode, only the elastically scattered component of the received Raman scattered light can be removed, and components other than the elastically scattered component can be analyzed with higher accuracy.

[0094] The meteorological observation optical radar (hereinafter referred to as "Raman optical radar") that detects Raman scattered light uses the temperature dependence of rotational Raman scattering or vibrational Raman scattering of nitrogen molecules and oxygen molecules to estimate the temperature. The detection of Raman scattering spectrum has the following advantages: the multi-wavelength method can be used to simultaneously capture the shapes of both the Stokes component and the anti-Stokes component of the Raman spectrum through the spectroscopic element and the array detector as described above. In this method, the robustness against wavelength deviation is high, and the measurement wavelength can be adjusted by changing the angle of the diffraction grating, so a high-level optical system setting technology is not required.

[0095] In Raman optical radar, when estimating the air temperature from the obtained Raman scattering signal, a measurement method independent of the Raman optical radar, such as the use of a radiosonde, needs to be calibrated. On the other hand, as described above, the simultaneous counting loss and crosstalk of the array detector are likely to affect the measurement results. In particular, in the rotational Raman spectrum, there are multiple positions where the intensities of adjacent channels are different by more than one order of magnitude. In Raman optical radar, in particular, the influence of crosstalk cannot be ignored in channels with weak signals, and the accuracy of air temperature estimation will be reduced. Therefore, in the past, correction values ​​(signal strength modification) were set not only for the air temperature but also for each measured signal intensity, and the correction values ​​obtained by linear interpolation were used to calculate the air temperature.

[0096] In addition, there is the following problem: since the calibration based on the comparison with the radiosonde is affected by the atmosphere and the measurement distance, the period required for the calibration becomes longer and the number of observations of the radiosonde increases. For these problems, a ground calibration device associated with a Raman optical radar is proposed that can obtain a rotational Raman spectrum with only the air temperature as a function (Yoichiro Fujita, Masanori Yabuki, Toshikazu Hasegawa, Eiji Takeuchi: Ground-based calibration of rotational Raman lidar for profiling atmospherictemperature, 2020AGU fall meeting, 2020.). In such a ground calibration device, a device for precise temperature adjustment is set in a small space on the laser axis before irradiation to the atmosphere, and the Raman spectrum of each air temperature is obtained based on its side scattering.

[0097] The inventors have found that in a weather observation optical radar equipped with a ground correction device as described above, simultaneous counting loss and crosstalk of the array detector are likely to affect the accuracy of the correction. In addition, the inventors have found that by using the optical radar light receiving device of this embodiment as a light receiving device, the influence of simultaneous counting loss and crosstalk on the measurement results can be reduced, and a weather observation optical radar that does not require high-precision correction can be provided.

[0098] Therefore, the weather observation optical radar of this embodiment may also include a ground correction device. The ground correction device is a device that is set in the optical path of the laser before the light is irradiated from the laser device to the sky, and is used to obtain the Raman spectrum, especially the rotation Raman spectrum, of each temperature based on the side scattering. The ground correction device may include, for example, a temperature control device for controlling the temperature inside the correction device, a temperature and humidity meter for measuring the temperature and humidity inside the correction device, and a light receiving unit for receiving scattered light of the light generated inside the correction device.

[0099] Figure 6 An example of the configuration of an optical radar equipped with a ground correction device is shown. Figure 6 As shown in FIG. 1 , the optical radar 200 includes an irradiation device 1A and a light receiving device 2A. The irradiation device 1A includes a ground correction device 16 between the laser device 10 and the mirror 12. Figure 1The ground correction device 16 includes a temperature control device 162 for controlling the temperature inside the device, a temperature and humidity meter 164 for measuring the temperature and humidity inside the device, and a light receiving unit 166 for receiving scattered light generated inside the device. The light from the light receiving unit 166 is guided to the light receiving device 2A through the optical fiber 28a. The temperature control device 162 may have a structure for circulating a heat medium whose temperature has been appropriately adjusted around the optical path of the laser. The light from the light receiving unit 20 of the light receiving device 2A and the light from the light receiving unit 166 are guided to the spectroscopic element 22 through the optical fiber coupler 28b. Figure 1 The light receiving device 2 of the optical radar 100 shown is different.

[0100] The above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit and explain the present invention. The various elements and their configurations, materials, conditions, shapes, and sizes of the embodiments are not limited to those shown in the examples, and may be appropriately changed. In addition, the structures shown in different embodiments may be partially replaced or combined with each other.

[0101] [Note]

[0102] The present invention includes the following embodiments. [1]

[0104] A light receiving device for an optical radar is a light receiving device for an optical radar for detecting scattered light of laser light, wherein:

[0105] The optical radar light receiving device comprises:

[0106] A spectroscopic element that splits the received light in such a way as to disperse the received light along one axial wavelength;

[0107] an optical element that makes the wavelength resolution of light with relatively high intensity in the split light higher than the wavelength resolution of light with relatively low intensity in the split light; and

[0108] An array detector detects light whose spectrum has been changed by passing through the optical element. [2]

[0110] The optical radar light receiving device according to [1], wherein:

[0111] The split light has a spectrum shape in which the intensity near the central wavelength is relatively high and the intensity near the spectrum end is relatively low. [3]

[0113] The optical radar light receiving device according to [1] or [2], wherein:

[0114] The optical element allows light L having a wavelength near the center wavelength of the spectrum among the split light. c The wavelength resolution of the wavelength dispersion axis of the light after being split is higher than that of the light having a wavelength near the spectral end of the spectrum. e The wavelength resolution in the axial direction of the wavelength dispersion of the light after being split. [4]

[0116] The optical radar light receiving device according to any one of [1] to [3], wherein:

[0117] The optical element increases the light L c The wavelength resolution of the wavelength dispersion axis of the light after being split is reduced by e The wavelength resolution in the axial direction of the wavelength dispersion of the light after being split. [5]

[0119] The optical radar light receiving device according to any one of [1] to [4], wherein:

[0120] The optical element is an aspherical lens, or a combination of an aspherical lens and one or more other optical elements. [6]

[0122] The optical radar light receiving device according to [5], wherein:

[0123] When the straight direction of the light after the splitting is defined as the z-axis direction and the wavelength dispersion axis direction of the light after the splitting is defined as the y-axis direction,

[0124] The aspheric lens is configured such that, when viewed from the x-axis direction orthogonal to the z-axis and the y-axis, the optical axis is aligned with the optical L. c The optical paths are roughly the same.

[0125] The aspherical lens makes the wavelength resolution in the y-axis direction of light passing through the vicinity of the optical axis higher than the wavelength resolution in the y-axis direction of light passing through a portion far from the optical axis in the y-axis direction. [7]

[0127] The optical radar light receiving device according to [6], wherein:

[0128] The aspherical lens is a cylindrical lens extending along the x-axis direction. [8]

[0130] The optical radar light receiving device according to any one of [1] to [7], wherein:

[0131] The beam splitting element includes a diffraction grating. [9]

[0133] The optical radar light receiving device according to any one of [1] to [8], wherein:

[0134] The optical element is a relay lens disposed immediately before the array detector.

[10]

[0136] The optical radar light receiving device according to any one of [1] to [9], wherein:

[0137] The optical radar light receiving device is used for meteorological observation.

[11]

[0139] An optical radar, wherein

[0140] The optical radar has:

[0141] an irradiation device that irradiates laser light; and

[0142] A light receiving device for an optical radar as described in any one of [1] to

[10] .

[12]

[0144] A meteorological observation optical radar, wherein:

[0145] The meteorological observation optical radar has:

[0146] an irradiation device that irradiates laser light into the air; and

[0147] A light receiving device for an optical radar as described in any one of [1] to

[10] .

[13]

[0149] The meteorological observation optical radar according to

[12] , wherein:

[0150] The laser light irradiated by the irradiation device is a laser light in the UV region.

[14]

[0152] The meteorological observation optical radar according to

[12] or

[13] , wherein:

[0153] The meteorological observation optical radar is used for air temperature measurement.

[0154] [Example]

[0155] Hereinafter, the present invention will be described in more detail using Examples and Comparative Examples. The present invention is not limited to the following Examples.

[0156] Simulation using OpticStudio and confirmation of light focusing using a CCD image sensor were performed. Figure 7 The model assumes focusing. The detection area is set to a maximum of 10 mm. Assuming that each channel of the array detector is composed of an effective width of 0.8 mm and a partition of 0.2 mm, 10 mm is equivalent to ten channels. It should be noted that each spot beam in the array detector is set to f = 500 mm and is focused in the y-axis direction.

[0157] In order to confirm the actual focusing state of the optical radar light receiving device, a laser with a wavelength of 354.7nm was injected, and a CCD (shooting area: 6.34mm (H) x 4.75mm (V)) was placed at the detector position to take pictures. Figure 8 The two beam splitters (2400mm -1 and 3600mm -1 diffraction grating) system. Figure 8 In (A), CCD represents a CCD image sensor, and other reference numerals are the same as above. Figure 8 As shown in (B) in FIG. 1 , the distance from the concave mirror 242 to the CCD is set to 500 mm. As a result, Figure 8 As shown in (C), in the CCD, the focusing point of each optical fiber is confirmed, and it is confirmed that the focusing position corresponds to the angle setting of the diffraction grating ( Figure 8 The line width of each spot beam is 0.98 mm, and the set wavelength range that can be measured within the shooting width of 6.34 mm is 4.9 nm.

[0158] Next, try inserting a concave-convex cylindrical lens just before the detector to expand the y-axis focusing position. Fig. 9 As shown in (A), Figure 7 In the setting, a concave lens and a convex lens with f=100 mm are arranged so that the detection position is set from the initial focus position ( Figure 7 The result is that if Fig. 9 As shown in (B) in Figure 7 Compared with (C), the interval between each spot beam is doubled, and it is confirmed that there is no significant effect on the spot beam radius.

[0159] Next, the influence of lens insertion was also confirmed in an actual optical radar light receiving device. Figure 8 Between the concave mirror 242 and the CCD in (A), as shown in FIG. Fig.10 As shown in (A), a cylindrical lens with concave and convex surfaces is inserted. Fig.10(B) in the figure shows the result of shooting based on CCD. The position of CCD is offset from the focusing position in the vertical direction (x axis), so the image is not visible. Figure 8 The focal point of each optical fiber is as shown in (C) in the figure, but it is confirmed that the light is focused rather than diverging in the horizontal direction (y axis). The line width of each spot beam is 0.72mm, and the set wavelength range that can be measured within the shooting width of 6.34mm is 4.0nm. Figure 8 When the result of (C) is compared with that of (C), the wavelength range that can be measured within the same imaging width becomes 0.82 times, and it can be confirmed that the wavelength resolution is reduced compared with the case without a lens.

[0160] Next, in Fig. 9 In the setting of (A), the cylindrical convex lens immediately in front of the detector is set as an aspherical cylindrical convex lens on the front surface and the rear surface. Fig.11 The simulation was performed in the setting of (A) in the above formula. As an aspheric lens, a lens having the coefficients shown in Table 1 was used in the aspheric lens function represented by the above formula (1). It should be noted that in Table 1, S1 is the surface on the concave lens side, and S2 is the surface on the array detector side. As a result, it is known that Fig.11 As shown in (B) in the figure, the light that has passed through the center of the lens is dispersed into multiple channels, and the light that has passed through the end of the lens is focused by combining the wavelength region. It should be noted that by changing the curvature of the two ends and the center of the lens, the focusing channel of each wavelength can be changed, but the lens can also be divided into multiple pieces when the curvature becomes larger.

[0161] [Table 1]

[0162]

[0163] Finally, suppose that the optical element that changes the wavelength resolution is arranged in the relay lens just before the array detector, so as to use Fig.12 (A) and Fig.12 The relay lens setting shown in (B) is simulated. Fig.12 (A) and Fig.12 In (B), the leftmost end is the position where the detector is originally arranged (the original image forming position of the spectroscopic element), and the rightmost end is the position where the detector is actually arranged. Fig.12 (A) is a top view of the relay lens (viewed from the x-axis direction). Fig.12 (B) is a side view of the relay lens (viewed from the y-axis direction). The relay lens is composed of six cylindrical lenses. Fig.12 (A) and Fig.12From the left of (B) in FIG. 1 , there are cylindrical lenses extending along the x-axis, x-axis, y-axis, x-axis, y-axis, and x-axis directions. In addition, the leftmost end is an aspherical cylindrical lens, and the others are spherical cylindrical lenses. Fig.12 (A) and Fig.12 As shown in (B) in the figure, the curved surfaces of each lens are set to S3~S8 in order from left to right, S3 is an aspherical surface having the coefficient shown in Table 2 in the aspherical lens function represented by the above formula (1), and each surface of S4~S8 is a spherical surface having the curvature radius shown in Table 2.

[0164] [Table 2]

[0165]

[0166] Fig.12 (C) in the figure shows the simulation results. Fig.12 (C) in the figure shows the distribution of the change in wavelength resolution along the y-axis before and after the incident light is incident on the relay lens. Each plotted point on the graph shows the ratio of the wavelength width contained in each unit length in the y-axis direction before and after the incident light is incident on the relay lens. It shows that the wavelength resolution in the center (near y = 0) becomes higher (becomes smaller as a numerical value) and the wavelength resolution becomes lower (becomes larger as a numerical value) at the ends.

[0167] Next, we simulated the effect of changing the optical radar light receiving device on the temperature measurement accuracy. -1 With 3600mm -1 The wavelength resolution (0.42 nm) of the two diffraction gratings is used as a benchmark. By introducing an optical element in front of the array detector to change the spectrum on the array detector, the temperature measurement accuracy of the meteorological observation optical radar changes to what extent. Fig.13 Indicates the wavelength setting of each channel of the array detector.

[0168] exist Fig.13 In the case 1 to 6, the wavelength setting is assumed to be obtained by setting the optical radar light receiving device shown in the following table. It should be noted that the aspheric lens 1 in Table 3 is a lens having the coefficients shown in Table 1 in the aspheric lens function represented by the above formula (1).

[0169] [Table 3]

[0170]

[0171] Fig.14It represents the signal intensity distribution of the rotational Raman spectrum obtained by irradiating a laser with a wavelength of 266nm and setting each detector. There is a tendency that the lower the temperature, the greater the intensity difference of each channel. It should be noted that, here, the focus is on the wavelength resolution of the detector, so only the detection settings of the detector (the effective width of each channel is 0.8mm, the partition is 0.2mm), and the signal intensity dependence based on simultaneous counting loss and crosstalk are considered, ignoring the laser wavelength fluctuation and the deviation of the center position of the detection wavelength. In addition, assuming that the correction signal for air temperature estimation is obtained when the channel with the maximum signal intensity is 20MHz, the case where the same channel of the observation signal is changed to 2 to 100MHz is calculated. The signal used for air temperature estimation uses the signal from the channel with the maximum signal intensity to the channel with 1 / 20.

[0172] first, Fig.15 The temperature estimation when the signal strength is modified (case-1 to 5) is shown. The temperature (273K, 300K) is set when the observed value is the same signal strength (20MHz) as the calibration spectrum. As the difference between the calibration and observation signal strength increases, the estimation accuracy decreases. Fig.14 The smaller the signal strength difference of each channel shown, the better the estimation accuracy. In particular, it is known that for case-5, when T=300K, even without signal strength correction, the temperature can be obtained with an accuracy of less than 1K up to a signal strength ratio of four times (calibration signal: 20MHz, observation signal: 80MHz).

[0173] A detailed investigation was conducted on case-5, and the estimated accuracy was calculated when the air temperature was assumed to be 250K to 320K ( Fig.16 ). In the case-5 setting, even without intensity modification, high-precision estimation can be performed without relying on signal intensity. This means that the lens design is effective according to the temperature range set as the observation object. In temperature estimation, the correction for signal intensity modification becomes the main factor determining accuracy. Therefore, if its influence can be reduced, it is related to reducing the correction frequency, expanding to various places, and expanding the observation altitude range.

[0174] Next, Fig.17 as well as Fig.18 The temperature estimation accuracy and deviation (case-1 to 6) after the signal strength modification is close to the actual operation are shown respectively. Here, the statistical estimation is based on the influence of the error of the signal strength modification value, so the signal strength modification value is given a normal distribution error of 1σ=5%, and the calculation is performed 100 times for each signal strength. Fig.14The smaller the signal with the smaller intensity difference of the rotation Raman spectrum, the better the estimation accuracy. It is known from the above simulation that when the signal intensity during calibration is greatly different from the intensity of the observed signal, the temperature estimation accuracy can be improved by 2 to 5 times or more by introducing an aspherical lens. It is expected that this method can improve the accuracy by inserting only a few lenses in the current setting, thereby reducing costs.

[0175] Description of Reference Numerals

[0176] 1. 1A: irradiation device;

[0177] 2. 2A: light receiving device;

[0178] 10: Laser device;

[0179] 12, 26: mirror;

[0180] 14: beam expander;

[0181] 16: Ground correction device;

[0182] 20, 166: light receiving part;

[0183] 21: aperture;

[0184] 22, 27: Spectral element;

[0185] 23: Signal processing unit;

[0186] 25: Slit;

[0187] 28a: optical fiber;

[0188] 28b: Fiber optic coupler;

[0189] 29: Remove components;

[0190] 100, 200: optical radar;

[0191] 162: Temperature control device;

[0192] 164: Thermohygrometer;

[0193] 231: Aspheric lens;

[0194] 232: array detector;

[0195] 233: Optical components;

[0196] 241, 242, 243, 244: Concave mirrors.

Claims

1. A light receiving device for an optical radar, which is a light receiving device for an optical radar for detecting scattered light of laser light, wherein: The optical radar light receiving device comprises: A spectroscopic element that splits the received light in such a way as to disperse the received light along one axial wavelength; An optical element that makes the wavelength resolution of light with relatively high intensity in the split light higher than the wavelength resolution of light with relatively low intensity in the split light; as well as An array detector detects light whose spectrum has been changed by passing through the optical element.

2. The optical radar light receiving device according to claim 1, wherein: The split light has a spectrum shape in which the intensity near the central wavelength is relatively high and the intensity near the spectrum end is relatively low.

3. The optical radar light receiving device according to claim 2, wherein: The optical element allows light L having a wavelength near the center wavelength of the spectrum among the split light. c The wavelength resolution of the wavelength dispersion axis of the light after being split is higher than that of the light having a wavelength near the spectral end of the spectrum. e The wavelength resolution in the axial direction of the wavelength dispersion of the light after being split.

4. The optical radar light receiving device according to claim 3, wherein: The optical element increases the light L c The wavelength resolution of the wavelength dispersion axis of the light after being split is reduced by e The wavelength resolution in the axial direction of the wavelength dispersion of the light after being split.

5. The optical radar light receiving device according to claim 3, wherein: The optical element is an aspherical lens, or a combination of an aspherical lens and one or more other optical elements.

6. The optical radar light receiving device according to claim 5, wherein: When the straight direction of the light after the splitting is defined as the z-axis direction and the wavelength dispersion axis direction of the light after the splitting is defined as the y-axis direction, The aspheric lens is configured such that, when viewed from the x-axis direction orthogonal to the z-axis and the y-axis, the optical axis is aligned with the optical L. c The optical paths are roughly the same. The aspherical lens makes the wavelength resolution in the y-axis direction of light passing through the vicinity of the optical axis higher than the wavelength resolution in the y-axis direction of light passing through a portion far from the optical axis in the y-axis direction.

7. The optical radar light receiving device according to claim 6, wherein: The aspherical lens is a cylindrical lens extending along the x-axis direction.

8. The optical radar light receiving device according to claim 1, wherein: The beam splitting element includes a diffraction grating.

9. The optical radar light receiving device according to claim 1, wherein: The optical element is a relay lens disposed immediately before the array detector.

10. The optical radar light receiving device according to any one of claims 1 to 9, wherein: The optical radar light receiving device is used for meteorological observation.

11. An optical radar, wherein: The optical radar has: an irradiation device that irradiates laser light; and A light receiving device for an optical radar according to any one of claims 1 to 9.

12. A meteorological observation optical radar, wherein: The meteorological observation optical radar has: an irradiation device that irradiates laser light into the air; and The light receiving device for optical radar as claimed in claim 10.

13. The weather observation optical radar according to claim 12, wherein: The laser light irradiated by the irradiation device is a laser light in the UV region.

14. The weather observation optical radar according to claim 13, wherein: The meteorological observation optical radar is used for air temperature measurement.

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